Bending of models combining beam & plate elements

[Anonymous]

Hi everyone,

I have built a model of a telescoping deck using a combination of beam and plate elements which is giving me some results I did not expect..... The deck comprises longituninal and crosswise PFC members (beam elements) with a 6 mm deck (plate elements) welded on top. I have offset the PFC by half their height so that their neutral axis is the requisite distance from the deck plate.

There are wheels at the rear and in the middle of the deck. I have constrained the model vertically at the wheels - and laterally at the rear wheels only. I have constrained the model longitudinally at a single node, through the centre, towards the rear of the deck - which simulates a cylinder connection point. The load is applied towards the front of the deck. In essence what this leaves is a structure with a cantilever load held laterally and longitudinally towards the rear, and vertically at the wheels. The central wheels are free to move forwards.

The front of the deck is 2700mm from the front wheels, and the load centre is 1200mm forward of the wheels. The load is around 13 te - and induces a deflection of 100mm. I know this is about right from physical tests we have carried out. The thing I'm really struggling with is that the longitudinal beams near the wheels are seeing a huge (22 te) tensile load (compressive) and given there are no applied longitudinal loads I'm wondering where this is coming from? Even taking into consideration 'stretch' due to deflection this load is very much larger than seems feasible... So I'm wondering;

1. If anyone has experience of such a situation.

2. If anyone has an explanation they can share - even a wild guess would be helpful

I am wondering about the interaction of beam and plate elements in bending - does that get anybody's grey matter churning?

It's monday of course, which isn't helping!

Any thoughts gratefully recieved

Regards, Debbie Wood

[zhuangs]

Beam elements resist moments, such as twisting and bending, at the connections.  However, truss elements only transimit axial forces.

-Shoubing